st: Adjusted Standard Error in QIC Program

[Kenneth Shermock <kshermo1@jhmi.edu>]

I ran the user-developed QIC program today on a dataset and got puzzling
results.  First the output when using the xtgee command:
xtgee out70250day group initgluccat unstablesocialhistory
intx_unstablesocialhistory, family(binomial) link(logit) corr(ar1) force

For our main variable of interest:
Coeff=3D -0.50045
Std err =3D 0.2235
P=0.025

I expected the results from the QIC program to be the same, but they are
not.

Output when using QIC program:
qic out70250day group initgluccat unstablesocialhistory
intx_unstablesocialhistory, i(mrn) t(date)family(binomial) link(logit)
corr(ar1) force

For our main variable of interest:

Coeff=3D -0.50045
Std err =3D 0.3062
P=0.102

I'm wondering if there is some glitch or if these results seem plausible.
The only difference I see between the QIC and xtgee models is the QIC
model "adjusts the std error for clustering" on one of my variables.  What
is this adjustment and is it plausible that it has such a profound effect
on model estimates?


Best regards,

Ken

Kenneth M. Shermock, PharmD, PhD
Director, Center for Pharmaceutical Outcomes and Policy
The Johns Hopkins Hospital

Core Faculty
The Armstrong Institute for Patient Safety and Quality
Johns Hopkins Medicine

600 North Wolfe Street
Carnegie 180
Baltimore, MD  21287
410-502-7674 (Desk)
410-955-0287 (Fax)
kenneth@jhmi.edu


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